I. Field
The present disclosure relates generally to electronics, and more specifically to a digital phase-locked loop (DPLL) with two-point modulation.
II. Background
A DPLL is a circuit commonly used to adjust the frequency and/or phase of an oscillator. In one common application, a DPLL may be used to lock the frequency and/or phase of an oscillator to a reference signal having a precise frequency.
In another application, a DPLL may be used to modulate the frequency and/or phase of an oscillator with a modulating signal. If the bandwidth of the modulating signal is much smaller than a closed-loop bandwidth of the DPLL, then the modulating signal may be applied prior to a loop filter within the DPLL. However, if the bandwidth of the modulating signal is wider than the closed-loop bandwidth, then two-point modulation may be performed, and the modulating signal may be applied to two modulation paths in the DPLL. One modulation path may be connected prior to the loop filter and may be used for narrowband modulation. The other modulation path may be connected after the loop filter and may be used for wideband modulation. Two-point modulation may be used to effectively increase the bandwidth of the DPLL, so that the oscillator can be frequency modulated with a wideband modulating signal while minimally disturbing the normal operation of the DPLL. However, the performance of two-point modulation is dependent on the proper gain and delay being applied for each modulation path.